1. Field of Invention
This invention relates generally to outboard motors and, specifically, to improvements in the shifting mechanisms for outboard motors which enable an operator to selectively choose forward, neutral, or reverse gear.
2. Description of the Prior Art
The inventor has had considerable experience with two popular makes of outboard motors and, particularly, with models manufactured between 1964 and the present time. He has found these motors to be excellent in substantially every category. However, there has been one area of difficulty which has persisted, at least within the realm of experience of himself and his associates. Specifically, it has been his experience that the shifting mechanisms of new motors often fail within a reasonably short period after being placed in service, oftentimes while the period of the warranty is still in effect. As time passes, with added usage and resultant wear, it becomes more and more difficult for an operator to maintain the shifting mechanism engaged in forward gear. Because reverse gear is used much less frequently than forward gear, breakdowns in that mode do not usually occur as readily. However, even with the reverse gear, eventually the wear will become such that the shifting mechanism will fail to maintain the reverse position.
In constructions which are known or commonly used, drive mechanisms for outboard motors utilize a shifting mechanism for selective movement between idle and forward and reverse modes of operation. In such conventional constructions, the so-called lower unit of an outboard motor incorporates a drive shaft pinion which rotates constantly and drives a pair of opposed bevel gears which are freely rotatable on the propeller shaft. A shifter is splined to the propeller shaft between the bevel gears and has a pair of integral dogs positioned at diametrically opposite locations on its opposed faces which are engageable, respectively, with mating lands integral with the bevel gears. The mating lateral surfaces of the dogs and lands, respectively, as conventionally known, lie in planes generally parallel to the axis of the propeller shaft.
The lateral and outer surfaces of the dogs and of the lands lie in generally transverse planes which intersect at an edge. In a new motor, the edge defined by the intersection between the lateral and outer surfaces is relatively sharp and clearly defines the limits of the respective surfaces. Hence, when the dogs of the shifter and corresponding lands of the bevel gears are brought into engagement, they remain in engagement until they are selectively disengaged by the operator. However, with continued usage, the lateral and outer surfaces become worn as does the edge between them. Such wear causes the mating surfaces of the dogs on the shifter and the lands on the bevel gears to slide relative to one another and, eventually, to slip apart and prevent further engagement.
Various attempts have been made by the manufacturers and operators of the motors to correct the above-described condition. In some instances, a spring pressed ball and associated detent have been employed to hold the shifter in a position such that its dogs are forced to maintain engagement with the lands on the bevel gear. In other instances, a stop or detent on the link of the upper shift control or operating handle adjacent the powerhead of the motor has been employed to aid against the dogs on the shifter from disengaging the lands on the bevel gear. Various and sundry adjustments have also been employed on the upper shift control or operating handle in its operative movement between the forward, neutral, and reverse positions. In most instances, these prior corrective approaches to the problem have been expensive, complex, difficult to maintain, and have generally failed to solve the basic problem.